1) Field of the Invention
The invention relates to a particle-optical apparatus and, in particular, to an electron microscopy system comprising such a particle-optical apparatus for examining an object.
2) Brief Description of Related Art
In an electron microscopy system, in order to examine an object, a primary electron beam is directed to the object to be examined and secondary electrons emanating from the object are directed as secondary electron beam to a detector and detected there. An image of the object under examination can be generated from an intensity of the detected secondary electrons.
In the present application, the term “secondary electrons” embraces, among others, also mirror electrons which are primary electrons reflected at the object which do not fully reach the surface of the object, as well as backscattering electrons which are electrons emitted from the surface of the object and have substantially the same kinetic energy as the primary electrons directed to the object, as well as secondary electrons in a narrower sense, that is, electrons emitted from the object which have a lower kinetic energy than the primary electrons directed to the object.
In electron microscopy systems, there is a need to select both the electrons of the primary electron beam and the electrons of the secondary electron beam in respect of their energy and to shape the electrons contained in the respective beam in respect of their energy spectrum and, in particular, to limit the same to a selectable energy range.
Moreover, there is a need to separate a beam path of the primary electron beam from the beam path of the secondary electron beam in order to be able to manipulate the beams as far as possible independent from each other. A possible manipulation may also comprise the above-mentioned energy selection.